RSA實現

Question

我正在研究rsa實現。 我想我已經快完成了，我偶爾遇到一個錯誤，在我運行代碼時，這是在shell中彈出的錯誤：

追溯（最近一次通話）：

File "/home/damion/Documents/projects/project2.py", line 164, in <module>
  decrypt_message = decrypt(encrypted_message,d,n)# decrypt message that was encrypted.
File "/home/damion/Documents/projects/project2.py", line 115, in decrypt
  decrypt_string+=DecimalToChar(m)#add each charactor to a string
File "/home/damion/Documents/projects/project2.py", line 96, in DecimalToChar
  return str(chr(d))
ValueError: chr() arg not in range(256)

這是我的代碼：

from random import randint

def prime(n):
    for i in range(2,n):
        if n%i==0:
            return False
    return True

def isprime(n):
    """
        return true if n is a prime number and false otherwise"""
    if prime(n):
        return True
    else:
        return False
def prime_generator():
    primeone=12
    while not isprime(primeone):
        primeone=randint(11,5000)
        print primeone
    print "prime number is: "+str(primeone)

    primetwo = primeone
    primetwo+=1
    while not isprime(primetwo):
        primetwo+=1
    print primetwo
    return primeone,primetwo

def gcd(x,y):
    """
        use to calculate the greatest common divisible of x and y """
    if y == 0:
        return x
    else:
        return gcd(y,x%y)

def n(prime1,prime2):
    """
        calculte and return 'N' That is used to find phi(N),and that is also used as to
        make up the private and public key
        """
    return prime1*prime2

def caculatePhi(prime1,prime2):
    """
        calculate Phi(N) and return Phi(N)"""
    return (prime1-1)*(prime2-1)

def e_finder(e,phi):
    """
        calculate e for the public key and return Phi(n),e,n"""
    while True:
        if gcd(phi,e) == 1:# check to see if phi and e has no common factor except one(1)
            return e
        else:
            e +=2 #increment e by to if there is a gcd>1

def Extended_Euclidean_Algorithm(PHI, E):
    phi = PHI
    e = E
    A,X,previous_X,Y,previous_Y = phi,0,1,1,0
    while e != 0:

        temp = e
        quotient = int(phi/e)
        e = phi % e
        phi = temp

        temp = X
        phi = previous_X - quotient * X
        previous_X = temp

        temp = Y
        Y = previous_Y - quotient * Y
        previous_Y = temp

    return A + previous_Y


def generate_keys(E,D,N):
    e,d,n = E,D,N
    """Calcualte private key(d),generate keys and return these keys
        ie. public and private keys for encryption and decryption"""

    return {"public_key":{"e":e,"n":n}},{"private_key":{"d":d,"n":n}}

def CharToDecimal(char):
    """convert a charactor to its decimal value
        """
    c=char
    return int(ord(c))

def DecimalToChar(decimal):
    d=decimal
    return str(chr(d))


def encrypt(m,e,n):
    """encrypt message and return that encrypted message """
    encryped_string = ""
    encrypt_lst=[]
    for i in m:# loop through message, getting charactor at a time for encryption
        m_char = CharToDecimal(i)#convert each charactor to its decimal equivalent
        c=pow(m_char,e,n)#equivalent to c=(m**e)%n
        encrypt_lst.append(c) # add each encrypted charactor to a LIST
        encryped_string+=str(c)
    return encrypt_lst,encryped_string

def decrypt(c,d,n):
    """decrypt message and return that decrypted message"""
    decrypt_string = ""
    for i in c: #loop through LIST of encrypted values,for decryption index by index 
        m=pow(i,d,n)#equivalent to m=(i**d)%n
        decrypt_string+=DecimalToChar(m)#add each charactor to a string
    return decrypt_string

if __name__ == "__main__":
    """Main for excuting programme"""
    message = str(raw_input("Enter message to encrypt: "))
##    prime_one = int(raw_input("Please Enter First Prime Number: "))
##    prime_two = int(raw_input("Please Enter Second Prime Number: "))
##
    prime_one,prime_two = prime_generator()
    while (not isprime(prime_one) or not isprime(prime_two)):#prompt user to enter value if not prime
        print""
        print""
        print"_________________________________________________________"
        if not isprime(prime_one):print "first number was not prime!!!"
        if not isprime(prime_two):print "Second number was not prime!!!"
        print""
        print"_________________________________________________________"
        print""
        prime_one = int(raw_input("Please enter first prime nuber: "))
        prime_two = int(raw_input("Please enter second prime : "))


    while prime_one<11 or prime_two<11: # prompt user to re-enter prime if less than 11
        print""
        print""
        print"_________________________________________________________"
        if prime_one<11:print "first number  Must Be greater Than 10!!!"
        if prime_two<11:print "Second number Must Be greater Than 10!!!"
        print""
        print"_________________________________________________________"
        print""
        prime_one = int(raw_input("Please enter first prime nuber: "))
        prime_two = int(raw_input("Please enter second prime : "))

    n= n(prime_one,prime_two)
    phi = caculatePhi(prime_one,prime_two)
    e=e_finder(3,phi)
    d=Extended_Euclidean_Algorithm(phi,e)


    keys = generate_keys(e,d,n) #get generated keys(public and private) and store them in keys

    print "keys are: ",keys


    encrypted_message,encryped_string = encrypt(message,e,n)#encrypt message from user
    print "Encrypted string: "+str(encryped_string)#display string of encrypted input
    print encrypted_message
    decrypt_message = decrypt(encrypted_message,d,n)# decrypt message that was encrypted.
    print "Our message decrypted is: "+str(decrypt_message)

Answer 1

正如Korem所說，您正在DecimalToChar函數DecimalToChar非法值傳遞給chr 。 （堆棧跟蹤是您的朋友。請閱讀堆棧跟蹤。） DecimalToChar只是chr周圍的一個大而胖的包裝器，在Python 2中它僅接受一個無符號的一字節整數（0到255，包括0和255）。

您只需要在一個位置調用DecimalToChar ，參數為m ：

m=pow(i,d,n)#equivalent to m=(i**d)%n

這將僅偶然地向chr產生合法輸入（並且在這種情況下非常罕見）： i ** d可能很大，而n是兩個大質數的乘積。）

確保未知（非負）整數在給定范圍內的傳統方法是模除法，在這種情況下，類似於：

def DecimalToChar(decimal):
    d=decimal % 256
    return str(chr(d))

這樣可以避免您遇到的錯誤，但是我認為它不會解決您的程序。 一個更大的問題是： 為什么您首先認為m應該是有效的ASCII字節？

其他一些建議：

1. 全局名稱空間中有很多代碼。 （事實上，你垃圾你n -the功能，當您重用名稱n -the -產品-的-兩個大素數，這是一個錯誤。）獲取所有的爛攤子到合適的main功能。

2. 您有很多功能實際上並沒有做任何事情。 n是一個（要啟動時使用無用的神秘名稱）， CharToDecimal和DecimalToChar ，它們復制Python內置DecimalToChar ，但需要更多鍵入內容。

3. 您有很多代碼根本不執行任何操作。 前面提到的CharToDecimal在ord的輸出（ 總是一個整數）上調用int ，而DecimalToChar在chr的輸出（一個始終是字符串）的輸出上調用str 。 （它們也完全沒有理由重命名參數。） isprime只會返回任何prime 。 這樣的無用代碼可以包含錯誤，但是它永遠無法幫助您。

4. 一致性！ 函數和變量名，空格，文檔字符串，甚至注釋格式無處不在。 通過使您的良好代碼和不良代碼看起來同樣糟糕，這將隱藏錯誤。